Thanks for the ideas guys. I've spent a bit of time at mulsannescorner.com and some time looking at similar cars at various events. I also keep my ear on the ground with F1 (
Scarbs is good for that).
The wheel well ventilation is something I've been thinking of as it's an option on the car and there are sections to cut out on the body to make it nice and easy. I assume that the wheel wells are high pressure, hence venting out the top reduces the pressure, generating negative lift. I guess it probably helps drag too as the pressure must be venting somewhere and that must be to the side, increasing effective frontal area.
The exhaust is something I'd like to change to blow into the rear diffuser. I'm worried about overheating fibreglass and effects of a new exhaust length on power. It'll go hand-in-hand with a new diffuser and would assist in reducing exhaust noise, which can only help me in scrutineering! That brings me onto strakes. How do I know the right number? I understand that it's the vortices created next to the strakes that energise the flow and assist in creating the downforce, but more strakes won't always mean more downforce.
The intakes at the front don't appear to do anything - they just vent straight into the wheel wells. The whole underside of the front panel from a few inches ahead of the dash is just a big open cavity that my feet, the battery and allsorts sit in. I would assume that closing it up will reduce drag, forcing air over the clean body, rather than through the car, just like a grille block.
On enclosing the cockpit, I'd use a flexible material, rather than fibreglass as I want to retain the ability to take passengers.
I really appreciate all the assistance you guys give me - there's a lot of clever people in this forum and efficiency is as important in racing as it is in fuel economy.